Showing papers by "Bernd Plietker published in 2009"

The Ruthenium‐Catalyzed Hydrovinylation of Internal Alkynes by Acrylates: An Atom Economic Approach to Highly Substituted 1,3‐Dienes

Abstract: The use of transition-metal-catalyzed reactions often allows for an efficient construction of complex molecular building blocks. The expression “atom economic” has been coined for transformations in which every atom of the starting material is transferred into the final product and such transformations fulfill the requirements of sustainability as defined by the Brundtland report. With regard to this background our group has tried to combine both methodological development and synthetic application over the past few years. 4] In the course of a natural-product synthesis we sought a method that allowed fast access to highly substituted sorbic acid derivatives. To allow the desired total synthesis to be performed in a modular and versatile way and to enable ruthenium-catalyzed processes to be combined in a sequential manner the original report by Watanabe and later work by Uemura on the hydrovinylation of alkynes appeared particularly attractive (Scheme 1).

7,7-Dimethyl-4a-(3-methyl-2-buten-yl)-2-oxo-4a,5,6,7-tetra-hydro-2H-chromen-4-yl benzoate.

Abstract: An intra­molecular Claisen-like cyclization of ethyl 2-acet­oxy-4,4-dimethyl-1-(3-methyl­but-2-en­yl)cyclo­hex-2-enecarboxylate followed by dialkyl­ation yielded the bicyclic title compound, C23H26O4. In both of the fused six-membered rings exist fragments of four atoms which are planar, whereas the remaining two atoms deviate by up to 0.682 (3) A on one side of the plane of the ring containing an O atom and by up to 0.415 (3) A on opposite sides of the other ring. The dihedral anglebetween the planar fragments of the six-membered rings is 41.76 (10)°

The Reincarnation of the Hieber Anion [Fe(CO)3(NO)]- — A New Venue in Nucleophilic Metal Catalysis.

Abstract: Nowadays demand for selective, energy-efficient, and sustainable chemical transformations has spurred an increasing interest in the development of “sustainable metal catalysis”. This expression defines a type of catalytic transformation in which non-toxic, readily available and inexpensive, stable metal complexes are used for catalysis. The increasing prices for energy and noble metals, which are commonly used for catalysis, represent an economical and ecological dilemma. If the price for a catalyst exceeds the savings on the energy side an industrial application does not make sense. As a consequence of this dilemma, chemists are looking for exit strategies with catalysis by small organic molecules (organocatalysis) or by inexpensive, readily available metal complexes (sustainable metal catalysis) being the most prominent ones. It is an irony that these two major catalytic strategies are based on research that had been initiated several decades ago but was somehow forgotten. In the present Microreview, the story of the reincarnation of another forgotten metal complex species, that celebrates its 50th birthday this year, will be told, the [Fe(CO)3(NO)]– anion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Selective C—S Bond Formation via Fe‐Catalyzed Allylic Substitution.

Abstract: In contrast to the formation of C−O and C−N bonds it was only recently that the selective C−S bond formation by means of transition metal complexes moved more into the center of research. This is somewhat surprising given the fact that the sulfur atom in a functional group can possess different oxygenation levels which correspond to different chemical properties and reaction portfolios. Herein we wish to communicate a regioselective Fe-catalyzed allylic sulfonation that allows for the preparation of various chiral aryl allyl sulfones in good to excellent yields.

7,7-Dimethyl-3,3,4a-tris-(3-methyl-but-2-en-yl)-4a,5,6,7-tetra-hydro-2H-chromene-2,4(3H)-dione.

Abstract: The title compound, C26H38O3, was prepared by an intra­molecular Claisen-like cyclization of ethyl 2-acet­oxy-4,4-dimethyl-1-(3-methyl­but-2-en­yl)cyclo­hex-2-enecarboxyl­ate followed by dialkyl­ation One of the methyl groups is disordered over two sets of sites in a 067:033 ratio